From DE 103 48 960 A1, a transmission unit with at least two three-shaft planetary gearsets is known, for the distribution of a transmission input torque to at least two transmission output shafts. A respective shaft of one planetary gearset is connected to the transmission input shaft. In addition, a respective shaft of each planetary gearset constitutes one of the transmission output shafts and at least one other shaft of each planetary gearset is in active connection with a shaft of the other planetary gearset.
The active connection between the interconnected shafts of the planetary gearsets comprises a third planetary gearset, an annular gear of the third planetary gearset being connected with the one shaft, that of the first planetary gearset, and a solar gear with the other shaft, that of the second planetary gearset. Furthermore, a satellite gear of the third planetary gearset is fixed to and able to rotate on the housing and another satellite gear is in rotationally fixed connection with an output shaft of an electric machine.
Accordingly, an operating-condition-dependent torque of one shaft of the first or second planetary gearset can be supported via the active connection as a function of an operating condition of the respective other shaft of the second or first planetary gearset actively connected to it, in such manner that if a speed difference occurs between the output shafts of the transmission unit, a torque that changes this speed difference is applied to the planetary gearsets by virtue of the active connection.
Owing to the active connection between two shafts of the first two planetary gearsets and the possibility, in the area of the active connection, of imposing a torque from the electric machine in the area between the interconnected shafts of the two planetary gearsets, a drive torque from a drive engine of a drive train in a vehicle can be distributed in the vehicle's longitudinal direction between two axles of the vehicle, or in the vehicle's transverse direction between the wheels of one axle of a vehicle, with a variable degree of distribution.
DE 199 17 665 A1 discloses a hybrid drive for a vehicle, which has a first electric machine and a second electric machine permanently connected to a transmission input shaft, in a drive train between a combustion engine and a multi-speed vehicle transmission. Between the electric machines, each of which can be operated as a motor and as a generator, and the combustion engine, a clutch that can be engaged is arranged in each case.
The first electric machine is provided for starting the combustion engine and the second electric machine primarily for starting the vehicle off under electric power when the combustion engine is uncoupled. In addition, the second electric machine can also be operated as a starter for the combustion engine or as a generator for the electrical system, i.e., for charging the battery or to produce electric power for other consumers and to drive the hydraulic pump of the vehicle transmission and, if necessary, to drive other auxiliary aggregates, such as the climatization compressor, the power steering pump, the braking force amplifier, or the water pump.
The disadvantage of this, however, is that the total weight of the vehicle is large, owing to the presence of two electric machines.
If it is desired to distribute the drive torque provided by the hybrid drive in the vehicle's longitudinal direction between the axles of the vehicle or in the vehicle's transverse direction between the wheels of one axle with a variable degree of distribution, for example, there is the possibility of constructing the multi-speed vehicle transmission in the manner proposed in DE 103 48 960 A1.
However, because of the electric machine integrated in the transmission unit, this again leads to an increase of the vehicle's weight, which results in higher fuel consumption.
Accordingly, the purpose of the present invention is to provide a vehicle with low vehicle weight, in which a drive torque can be distributed with a variable degree of distribution in the vehicle's longitudinal direction between two vehicle axles or in its transverse direction between the wheels on a vehicle axle.